Effect of high hydrostatic pressure on free sulfhydryl content fromfungal α-amylase

Abstract

We evaluated the residual thermal effect generated by the consecutive High Hydrostatic Pressure (HHP) cycles relative to the position (upper, central and lower) inside a high pressure vessel determining the free sulfydryl groups [F-SH] from pressurized α-amylase Aspergillus oryzae expressed in μmol SH/g protein. Tis methodology could represent a potential indicator of HHP treatment, allowing to measure in an indirect way the thermal effect during the process. Assays were carried out using a 2L stabilized lab scale equipment, where pressurizing medium (water-propilenglycol:70-30%) was injected at room temperature from the bottom of the vessel. For each cycle, the fluid at room temperature was compressed until reaching the desired pressure (605 MPa), maintained for fve minutes, followed by depressurization. Te cycle was repeated three consecutive times. The free sulfydryl content was assayed statistically using one-way ANOVA (α=0,05) for a factorial design of two factors: positions and consecutive cycles, with three levels, and four repetitions for the complete design. Signifcant differences were obtained in the interaction cycles* position (pvalue = 0,001) and cycles (pvalue = 0,021). These results demonstrate the effect of the heat generation during adiabatic compression, affecting the thermal history of the α-amylase. Due to its sensitivity to pressure, this enzyme could be considered as a potential indicator of high pressure processing in the future, evaluating the difference between processed samples during cycles, and confrming the thermal profle generated within the equipment.